Allow a 'name' in the jam section in package.json

[ryanramage]

Sometimes you need to publish to jam a slightly different name than the original package.json defines. It would be nice to provide an override in the jam section, eg:

"jam" : {
     "name" : "something-else"
}

This helps in porting packages written for other package managers.

[caolan]

Sounds sensible.

[ryanramage]

Closing as PR was merged.